Spell Check was implemented in Release 0.60 - on 2/14/2016

If it is still greyed out, make sure you are running that release or higher

You can change your dictionary by going to:

  • File
  • Options
  • Spelling

If you want to spell check in an additional language, you will need to add it to your PC. See How to add an input language to your PC

There are additional options which should be self-explanatory